Radio Frequency (RF) catheter ablation for atrial fibrillation (AF) may prevent stroke, but paradoxically, the procedure itself can cause stroke or other ischemic cerebrovascular events. Cognitive dysfunction may arise in 13% to 20% of cases after cardiac ablation procedures, and MRI studies have identified between 7% and 38% incidences of silent ischemic lesions in the brain after ablation. Thromboembolic risks exist during many other procedures involving intravascular devices. For example, vascular sheaths, catheters, and other devices may benefit from technology preventing blood clots forming on blood contacting surfaces. FocusStart has developed such a technology, and has shown that application of a small negative charge successfully reduces coagulum formation on non-irrigated and irrigated RF ablation electrodes during cardiac ablation in vivo via a fibrinogen repelling mechanism. This technology could be used as an add-on device for all RF ablation catheters with the goal to reduce coagulum formation, and subsequent thromboembolic events. The negative charge technology by FocusStart may not only increase the safety of RF ablation procedures, but also increase procedural efficacy by enabling physicians to use higher RF energies without the risk of coagulum formation. This Direct Phase II SBIR proposal outlines research and development to bring this coagulum-prevention technology to clinical use. Aim 1 of the proposal is to study the effects of applying negative charge to cardiac RF ablation electrodes on coagulum formation (previously shown) and thromboembolic events (not previously shown). In acute canine left heart RF ablation studies, the effects of negative charge application on coagulum formation will be measured via intracardiac echography (ICE); any systemic thromboembolic events will be assessed simultaneously both via an extracorporal blood loop containing a filter, as well as real-time via Transcranial Doppler sonography. The effects of negative charge application on cerebrovascular events will be assessed in a chronic canine RF ablation model. In the chronic model, coagulum formation will be measured via ICE, thromboembolic events via Transcranial Doppler, and any cerebrovascular events will be assessed via neurological (behavioral) function, MRI imaging and histopathology. Aim 2 of this proposal is to further develop and validate the negative charge device for regulatory approval and clinical use.